Light that is projected onto a scene interacts with various objects within the scene by being reflected or transmitted at one or more boundaries of surfaces of such objects, or by being absorbed by such surfaces and dissipated as heat. Light typically reflects from surfaces of objects according to the law of reflection, which states that the angle of incidence of a ray with respect to a normal of a surface is equal to the angle of reflection of a ray with respect to the normal of the surface, such that an angle at which an incident ray arrives at a surface is equal to an angle from which a reflected ray departs from the surface.
Different materials may interact with incident light in different ways, and the appearance of such materials may vary given the same lighting conditions. For example, some materials or portions of surfaces thereof may appear as mirrors, and reflect substantial portions of the incident light, while other materials may appear as diffuse surfaces. A manner in which a material appears in the presence of incident light is typically driven by the reflectance properties of one or more surfaces of the material.
Specular reflection is the reflection of light from a smooth surface of an object, which thereby causes the incident rays to be reflected at common angles of reflection. Some common examples of specularly reflected light include visible light that is reflected from a pane of glass or a surface of a pond. Specular reflection may be particularly acute where the incident light originates from a single point, such as the sun, or from a single, particularly bright artificial light source. Diffuse reflection is the reflection of light from a coarse or rough surface of an object, which thereby causes the incident rays to be reflected at varying disparate angles of reflection. Some common examples of diffusely reflected light include visible light that is reflected from a paved roadway or a sandy beach.
An imaging device such as a digital camera operates by capturing information or data regarding light that is reflected from a surface of an object. The reflected light may originate either from the sun or from an artificial light source, e.g., an overhead or nearby light source (e.g., lamps or ceiling lights), as well as a flash mounted to the imaging device. Therefore, depending on the texture of the surface of the object that is being photographed, the light that is reflected from the surface may be diffusely reflected or specularly reflected.
When an imaging device such as a digital camera that is aligned in a particular location or at a particular orientation captures an image of an object that includes specularly reflected light, e.g., an object with extremely smooth and reflective surfaces, the sensor of the digital camera may be dominated by the concentrated nature of the specularly reflected rays, which may cause regions of pixels corresponding to the portions of a surface from which such specularly reflected rays originate within an image to be overexposed. The visual effects of the specular reflections within the image may further extend or spill over into other neighboring pixels, as well.